1-[(diorganooxyphosphonyl)methyl]-2,4,- and -2,6-diamino benzines and their derivatives

ABSTRACT

1-[(Diorganooxyphosphonyl)methyl]-2,4- and -2,6-dinitro- and diamino benzenes are prepared by nitrating an (organophosphonyl)methyl benzene to produce The dinitro compounds which are then reduced to the diamino compounds. The organo groups (alkyl, haloalkyl, aryl) on the phosphorus may be removed to give the free acids, (HO) 2  P(═O)--. The diamino compounds may be polymerized with dianhydrides or diacyl halides to produce fire and flame resistant polymers which are useful in the manufacture of aircraft structures.

ORIGIN OF THE INVENTION

The invention described herein was made in the performance of work undera NASA contract and is subject to the provisions of Section 305 of theNational Aeronautics and Space Act of 1958, Public Law 85-568 (72 Stat.435; 42 U.S.C. 2457).

RELATED APPLICATIONS

This application is a continuation-in-part of our copending applicationSer. No. 522,629, filed Aug. 12, 1983, now abandoned, which is directedto compounds and polymers having ##STR1## repeating units, which isincorporated herein by reference. The application is also related to thefollowing commonly assigned patent applications: U.S. Ser. No. 641,142,filed Aug. 16, 1984, which is directed to the above mentioned compoundsand polymers; U.S. Ser. No. 641,153, filed Aug. 16, 1984, which isdirected to polyamides prepared from the present diaminobenzenes; U.S.Ser. No. 641,143 filed Aug. 16, 1984, now U.S. Pat. No. 4,536,565, whichis directed to polyimides and copolyimides prepared from the presentdiaminobenzenes; and U.S. Ser. No. 641,147, filed Aug. 15, 1984. whichis directed to maleimido and citraconimido-substituted derivatives ofthe present diaminobenzenes.

FIELD OF THE INVENTION

The invention relates to 1-[(dihydroxy- anddiorganooxyphosphonyl)methyl]-2,4- and -2,6- dinitro benzenes, to thediamino products resulting from reduction of the nitro groups of theaforesaid dinitro compounds, to products (including mixtures andpolymers) of the dinitro compounds and to methods of preparation of thedihydroxy, dinitro and diamino compounds. The polymers of this inventionare fire and heat resistant having useful mechanical properties.

BACKGROUND OF THE INVENTION

Certain phosphorus-containing organic compounds are known to be fireretardant when mixed with or incorporated chemically in polymers. Amongsuch phosphorus-containing compounds are diamino compounds which can,for example, be polymerized with diacyl halides or dianhydrides. It isknown, for example, to incorporate phosphorus into2,4-dinitrochlorobenzene by reacting the latter with diethyl phosphiteresulting in 2,4-dinitrodiethoxy-phosphonyl benzene. By reducing thenitro groups, a diamine is produced. However, the yield of dinitroprecursor to the diamino species is low, e.g., about 11%.

Some references of the inventors, which describe fire resistantcompositions of phosphoruscontaining resins and the monomers thereof,include the following:

1. J. A. Mikroyannidis and D. A. Kourtides, "Fire-Resistant Compositionsof Epoxy Resins with Phosphorus Compounds", Symposium on Rubber-ModifiedThermoset Resins, 186th Annual American Chemical Society Meeting,Washington, D.C., Abstract PMSE 133, Aug. 28-Sept. 2, 1983;

2. J. A. Mikroyannidis and D. A. Kourtides, "Fire-Resistant Epoxy ResinsContaining 1-(Di(2-Chloroethoxy phosphinyl) Methyl)-2,4- and 2,6Diaminobenzene as Curing Agent", Proceedings of the 12th North AmericanThermal Analysis Society Conference, Williamsburg, Va. (September 1983);

3 J. A. Mikroyannidis and D. A. Kourtides, "Curing of Epoxy Resins with1-[Di(2-Chloroethoxyphosphinyl)Methyl]-2,4- and 2,6-Diaminobenzene",Journal of Applied Polymer Science, Vol. 29, pp. 197-209, (1984);

4. J. A. Mikroyannidis and D. A. Kourtides, "Curing of Epoxy Resins with1-[Di(2-Chloroethoxyphosphinyl)Methyl]-2,4- and 2,6-Diaminobenzene",National Aeronautics and Space Administration Report No. TM 84350,October 1983;

5. J. A. Mikroyannidis and D. A. Kourtides, "Synthesis andCharacterization of Phosphorus-Containing Polyamides and Copolyamidesbased on 1-[Dialkoxyphosphinyl)Methyl]-2,4- and -2,6-Diaminobenzenes",Journal of Applied Polymer Science, Vol. 29, pp. 941-953 (1984);

6. J. A. Mikroyannidis and D. A. Kourtides, "Synthesis andCharacterization of Phosphorus Containing Polyamides and CopolyamidesBased on 1-[(Dialkoxyphosphinyl) Methyl]-2,4- and -2,6-Diaminobenzenes",Proceedings of the Society for the Advancement of Materials and ProcessEngineering, Reno, Nev. (April 1984); and

7. J. A. Mikroyannidis and D. A. Kourtides, "Curing of Epoxy Resins with1-[Di(2-Chloroethoxyphosphinyl)Methyl]-2,4- and -2,6-Diaminobenzene",Proceedings of the Society of Plastics Industry Annual Spring Meeting,St. Louis, Mo. (May 1984).

These references are not considered to be prior art regarding thisinvention.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a route to flame retardantdiamino compounds containing phosphorus which is facile and providesgood yields. These compounds when combined with epoxys, etc. providepolymers which are useful for lamination, which combine good fire andheat resistance with good mechanical properties.

BRIEF SUMMARY OF THE INVENTION

In accordance with the invention a phosphonylmethylbenzene having thegeneral formula ##STR2## is provided and is polymerized with a monomersuch as an epoxide, a dianhydride, etc. In 1x the R groups may be thesame or different and they may be aliphatic, cycloaliphatic or aromatic,preferably being lower alkyl [methyl, ethyl, propyl (n and iso),etc.]and most advantageously contain a halogen such as chlorine. X and Yare functional groups which are polymerizable with, for example, epoxyor anhydride groups and they may be the same or different. Preferably Xand Y are amino groups and they will be predominantly in the 2- and4-positions relative to the phosphonyl methyl group. X and Y may also behydroxyl, carboxyl, etc.

The resulting polymers combine one or more properties of heatresistance, low flammability and high char yield with good mechanicalproperties such as high tensile strength.

The reaction mixture may include other species such as, for example, amixture of a diamine species of 1x, a conventional diamine such asm-phenylenediamine (MPD) or 4,4-diaminodiphenyl sulfone (DDS). Theseconventional species may serve to impart toughness and/or otherdesirable properties to the polymer.

In the invention, a phosphorus-containing precursor represented by theformula: ##STR3## i.e., a phosphonyl methyl benzene in which the twophosphonyl hydroxyl groups are protected by R groups which are alkylgroups, aryl groups, substituted alkyl groups or other suitableprotecting groups, is nitrated to produce a mixture of 2,4- and 2,6-dinitro compounds of the formula: ##STR4## in which the second nitrogroup is in the 4- or 6-position. The dinitro compounds 2 are thenreduced to produce the diamino compounds of the formula: ##STR5##

The protecting groups R may be removed by hydrolysis to produce thecorresponding phosphonyl acids, (HO)₂ P(═O)--, of 2 and 3. The two R'smay also be replaced by a single bivalent group.

The amino groups of 3 may be reacted with acyl halides, R'(C═O)--X, toproduce amides: ##STR6## where R' is an organic group, such as alkyl oraryl or alkaryl containing, for example, 1 to 8 carbon alkyls, such asmethyl, ethyl, butyl, cyclohexyl, octyl and 2-ethylhexyl, benzyl,phenyl, 2-ethylbenzyl, phenylethyl and the like, and X is a halo such aschloro or bromo.

The diamino compounds 3 may be polymerized with diacyl halides ordianhydrides to produce fire resistant thermoplastic polymers or withhigher functionality acyl halides or anhydrides to produce fireresistant cross linked polymers.

DETAILED DESCRIPTION OF THE INVENTION

The process of this invention begins with nitration of a protectedphosphonyl methyl benzene of the formula: ##STR7## The two protectinggroups R may be an alkyl, haloalkyl, or aryl group. Examples of R aremethyl, ethyl, n- and iso-propyl, higher (e.g., C4 to C10) alkyl;haloalkyls of the same chain length such as chloro or bromoalkyls,especially chloroalkyl, such as 2-chloroethyl; aromatic groups, such asphenyl, and the like. Other equivalent non-nitratable R groups may beused as well. The two R groups are usually identical and may if desiredbe a single alkylene such as from 3 to 6 carbons bridging and protectingboth phosphonyl hydroxyls. Preferred R groups are 1 to 4 carbon alkylsand haloalkyls and phenyls. Ethyl and 2-chloroethyl groups are the mostpreferred R groups.

Compound 1 may be produced by the Michaelis-Arbuzov reaction of benzylbromide with a suitable trialkylphosphite or other equivalent protectedphosphate. See, G. M. Kosolapoff and L. Maier, "Organic PhosphorusCompounds", Wiley Interscience, 1973, Vol. 7, page 184.

The nitration of compound 1 may be carried out by direct nitration. Thismay be effected by contacting the compound 1 with an excess beyond twoequivalents of nitric acid in fuming sulfuric acid under anhydrousconditions at elevated temperatures. Generally, the amount of nitricacid is from about 2.1 to about 10 moles per mole of nitratable benzenerings. The elevated temperature is typically from about 40° C. to about90° C., preferably about 45° C. to 65° C. This reaction generally takesfrom about 0.5 to about 8 hours to complete.

The product of this nitration is a mixture of 2,4 and 2,6 dinitrophosphonyl methyl benzenes of the formula: ##STR8## If desired, theisomers may be separated from one another, e.g., by crystallization, butfor many purposes such separation is not necessary. The 2,4-isomer isgreatly predominant and for most practical uses the mixture may beregarded as the 2,4-dinitro (and subsequent 2,4-diamino) compounds.

In the next step the dinitro compounds 2 are reduced to produce thediamino compounds of the formula: ##STR9## This reduction may be carriedout by any of the methods known to the art for reducing nitro-containingaromatic compounds. A preferred method is catalytic reduction usingmolecular hydrogen and a supported catalyst such as a supported noblemetal catalyst for example platinum or palladium on an inert organicoxidic support or carbon. This reduction is exothermic and can beconducted at temperatures from ambient (about 10° C.) to about 100° C.and hydrogen partial pressures of from about 1 atmosphere to 20atmospheres or more. The reaction is continued until no more hydrogen istaken up. The reduction is carried out with the dinitro compounddissolved in a non-aqueous medium, for example, a lower alkanol such asmethanol or ethanol.

The phosphonyl protecting groups "R" are acid labile and may be removedfrom either the dinitro compounds 2 or the diamino compounds 3 by acidichydrolysis to produce the corresponding phosphonyl acids, (HO)₂ P(═O)--.This hydrolysis is carried out in concentrated aqueous strong mineralacid, such as HCl, HBr or H₂ SO₄, at elevated temperatures such as about50° to 150° C. especially at reflux for from about 0.5 to 8 hours. Thisproduces the phosphonyl acids corresponding to compounds 2 and 3.

The amino groups of the compounds of 3 may be reacted with acyl halides,R'(C═O)--X, to produce amides: ##STR10## where R' is an organic group,such as alkyl or aryl or alkaryl, for example, 1 to 8 carbon alkyls,e.g., methyl, ethyl, butyl, cyclohexyl, octyl and 2-ethylhexyl, benzyl,phenyl, 2-ethylbenzyl, phenylethyl and the like, X is a halo such aschloro or bromo.

(Diamidophenyl)methyl phosphonic acid of the formula: ##STR11## where R'is selected from alkyls such as C1 to C10 (e.g., methyl) and aryls(e.g., phenyl) and the two amido groups are in the 2,4 or 2,6 positionsis prepared by reacting the compounds of formula 4 with strong aqueousmineral acid as described herein to selectively remove the R groups.Alternatively, the phosphonyl acids of structure 3 may be treated withthe corresponding acyl halides, R'(C═O)--X, described herein toselectively react with the amine groups.

The diamino compounds 3 and their phosphonyl acids have excellentproperties which give them several distinct utilities. The freephosphonic acids resulting from conversion of the dialkoxy groups tohydroxy groups may be used as complexing agents to extract metals fromaqueous solutions, and they can also be used as corrosion inhibitors formetals.

The diamines of the present invention may also be used as curing agentsfor epoxy resins. They may be polymerized and copolymerized with avariety of dianhydrides and diacylchlorides (and with higherfunctionality anhydrides and acylchlorides), e.g., pyromelliticanhydride, the dianhydride ##STR12## and isophthaloyl chloride,1,3--[(C═O)Cl]₂ φ.

These compounds are useful in the preparation of polymers which can beused as resin matrices for composites. The composites possess both hightemperature resistance and fire resistance. These laminating and matrixresins can be combined with either glass, KEVLAR® or graphite fibers inthe form of either unidirectional tape or fabric which in turn can befabricated into secondary composites, such as composite sandwich panelsfor aircraft interiors. Another application of these compounds is theuse of these resins as encapsulating or potting compounds when thecompounds are reacted with epoxy resins. These compounds will be moreflame and fire-resistant when compared with conventional epoxy resins.

The present invention will be further described with reference to thefollowing examples. These are presented to illustrate the invention andare not to be construed as limiting its scope which is defined by theappended claims.

EXAMPLE 1 1-[(Diethoxyphosphonyl)methyl]-2,4- and -2,6-dinitrobenzenes

[(Diethoxyphosphonyl)methyl]benzene (21.76 g, 95 mmol) was addeddropwise to a mixture of fuming nitric acid (16.3 g) and fumingsulphuric acid (54.30 g), containing 30% SO₃, at 55° C. The addition ofthe phosphonate lasted 1 hour and subsequently the mixture was heated atthe same temperature for another hour. The mixture was poured into 1liter of ice water and extracted with chloroform (300 ml). Thechloroform solution as washed with 5% sodium bicarbonate solution andwith water, dried (Na₂ SO₄) and concentrated to give a yellowish solid(24.16 g, 80%, mp 78°-82° C.). Recrystallizations from ether-chloroform(10:1 vol/vol) gave an analytical sample: mp 101°-104° C. The structurewas confirmed by ¹ H-NMR and chemical analysis.

EXAMPLE 2 1-[(Diethoxyphosphonyl)methyl-2,4- and -2,6-diaminobenzenes

The recrystallized product of Example 1 (2.00 g, 6.28 mmol) wasdissolved in 50 ml of absolute ethanol and a small amount of catalyst,10% palladium on carbon, was added. The hydrogenation was carried out ona Parr apparatus under a pressure of 3.5 atm at room temperature untilno more hydrogen was taken up (about 3 hrs). After the filtration of thecatalyst and the removal of the volatile components under vacuum aviscous undistillable liquid was obtained (1.57 g, 97%), which could notbe induced to crystallize.

The dihydrochloride salt was formed by passing anhydrous hydrochloridegas through its solution in chloroform. This salt was a nearly whitesolid and after recrystallizations from ethanol-ether (1:6 vol/vol) ananalytical sample was obtained which was decomposed at temperaturehigher than 128° C. Structure was confirmed by ¹ H-NMR and chemicalanalysis.

EXAMPLE 3 1-[(Diethoxyphosphonyl)methyl]-2,4- and-2,6-di(benzoylamino)benzenes

Recrystallized dihydrochloride salt of the product of Example 2 (2.19 g,6.6 mmol) and 20 ml of dried dichloromethane were placed in a flaskequipped with a condenser. The diamine was formed in situ by addition oftriethylamine (2.67 g, 26.4 mmol). Benzoylchloride (1.86 g, 13.2 mmol)was added to the mixture. An exothermic reaction was observed and themixture was stirred under nitrogen for 5 minutes into an ice bath. Thestirring was continued at room temperature for 2 hours. n-Hexane (about100 ml) was added to the mixture to reprecipitate the produceddibenzoylamino derivatives as well as the salt, Et₃ N.HCl. The mixtureof these compounds was treated at room temperature with benzene (about50 ml) which mainly dissolves the dibenzoylamines. Thus, the benzenefiltrate by concentration under vacuum gave a white solid (2.36 g, 77%,mp 230°-233° C.). An analytical sample was obtained byrecrystallizations from ethanol-acetonitrile (1:5 vol/vol), mp 231°-234°C. Structure was confirmed by ¹ H-NMR and chemical analysis.

EXAMPLE 4 1-[Di(2-chloroethoxyphosphonyl)methyl]-2,4- and-2,6-dinitrobenzenes

[Di(2-chloroethoxyphosphonyl)methyl]benzene (5.13 g, 17 mmol) was addeddropwise to a mixture of fuming nitric acid (4.0 g) and fuming sulphuricacid (13.0 g), containing 30% SO₃ at 55° C. The addition of thephosphonate lasted 0.5 hour and subsequently the mixture was heated atthe same temperature for 4 hours longer. The mixture was poured into 300ml of ice water and extracted with chloroform (150 ml). The chloroformsolution was washed with 5% sodium bicarbonate solution and with water,dried (Na₂ SO₄) and concentrated to give a viscous liquid (4.92 g) whichwas diluted with about 100 ml of acetone-ether (1:10 vol/vol). Uponcooling of the solution, the dinitrobenzenes were crystallized (2.80 g,42%, mp 79°-84° C.). Recrystallizations from acetone-ether (1:10vol/vol) gave an analytical sample: mp 83°-85° C. Structure wasconfirmed by ¹ H-NMR and chemical analysis.

EXAMPLE 5 [Di(2-chloroethoxyphosphonyl)methyl]-2,4- and-2,6-diaminobenzenes

Recrystallized product of Example 4 (2.27 g, 58.6 mmol) was dissolved in40 ml of absolute ethanol and a small amount of catalyst, 10% palladiumon carbon, was added. The hydrogenation was carried out as described inExample 2. A solid product was obtained (1.88 g, 98%, mp 105°-109° C.).Recrystallizations from benzene gave an analytical sample: mp 116°-119°C. Structure was confirmed by ¹ H-NMR and chemical analysis.

EXAMPLE 6 1-[Di(2-chloroethoxyphosphonyl)methyl]-2,4- and-2,6-di(benzoylamino)benzenes

Recrystallized product of Example 5 (0.44 g, 1.35 mmol), drieddichloromethane (15 ml), triethylamine (0.27 g, 2.7 mmol) and benzoylchloride (0.38 g, 2.7 mmol) were placed in a flask equipped with acondenser. The reaction as well as the isolation of the product wascarried out as in Example 3. A white solid was obtained (0.58 g, 80%, mp195°-198° C.). Structure was confirmed by ¹ H-NMR and chemical analysis.

EXAMPLE 7 1-[(Dihydroxyphosphonyl)methyl]-2,4- and -2,6-dinitrobenzenes

1-[(Diethoxyphosphonyl)methyl]-2,4- and -2,6-dinitrobenzenes (2.00 g,6.3 mmol) from Example 3, were dissolved in concentrated hydrochloricacid (20 ml), and the solution was refluxed for 4 hours. After removalof the volatile components of the mixture under vacuum a white solid wasobtained (1.30 g, 96%, mp 211°-214° C.). Recrystallizations fromacetoneether (1:4 vol/vol) gave an analytical sample: mp 217°-219° C.Structure was confirmed by ¹ H-NMR and chemical analysis.

EXAMPLE 8 Polymerization of a Diamino Monomer

The dihydrochloride salt of 1-[(diethoxyphosphonyl)methyl]-2,4- and-2,6-diaminobenzene (2.21 g, 6.66 mmol), the dihydrochloride salt ofm-phenylenediamine (6.21 g, 34.3 mmol), dimethylacetamide (70 ml) andpyridine (12.96 g, 163.84 mmol) were placed in a three-necked flaskequipped with a mechanical stirrer and a dropping funnel. The mixturewas stirred to obtain a solution and cooled to 0°-1° C. A solution ofisophthaloyl chloride (8.32 g, 40.96 mmol) in dimethylacetamide (30 ml)was added dropwise under nitrogen atmosphere allowing the reaction toproceed 10 minutes with cooling and then 60 minutes at room temperature.The reaction mixture was added to about 700 ml of methanol and theproduct which precipitated was filtered, washed repeatedly with methanoland dried at 80° C. in a vacuum oven. The polymer (9.70 g, 90%) had aninherent viscosity 0.22 dl/g in sulphuric acid 98% (0.5% conc. at 25°C.) and contained 1.44% phosphorus. This polymer had a Limiting OxygenIndex value 52.0 and an anerobic char yield at 700° C. 72%. Thepoly-m-phenylene isophthalamide (Nomex) which may be considered as itsparent polyamide had a Limited Oxygen Index 46.4 and an anerobic charyield 57%. (Oxygen index value was measured by the method of ASTM D2863-70. Anerobic char yield was that described by Van Krevolin,Polymer, Vol. 16, pp. 615 ff (1975).

While the present invention has been described with reference tospecific embodiments thereof, it will be understood by those skilled inthis art that various changes may be made and that equivalent steps maybe substituted without departing from the true spirit and scope of thepresent invention. All such modifications or changes are intended to beincluded within the scope of following claims.

We claim:
 1. A method of producing a (diorganooxyphosphonyl) methyldiamino benzene which comprises providing dinitro compounds of theformula: ##STR13## wherein R is an organo group selected form alkyls,having from C1 to C10 carbon atoms, phenyls, and halo-alkyls having fromC1 to C10 carbon atoms, and where the two R groups may be a singlealkylene having from 3 to 6 carbon atoms, and the two nitro groups arein the 2, 4 and 2, 6 positions, and subjecting said dinitro compounds toreduction conditions selected from molecular hydrogen with platinum oncatalyst support or molecular hydrogen with palladium on a catalystsupport at a pressure of between 1 and 20 atmospheres at a temperatureof between about 10° and 100° C. in a non-aqueous medium to producediamino compounds of the formula: ##STR14## wherein the two amino groupsare in the 2,4 and 2,6 positions.
 2. The method of claim 1 wherein R isselected from ethyl and 2-chloroethyl.
 3. The method of claim 2 whereinthe diamino compound is primarily the 2, 4-compound.
 4. A method ofproducing a (diorganooxyphosphonyl) methyl diamino benzene whichcomprises providing dinitro compounds of the formula: ##STR15## whereinR is an organo group selected from alkyls, phenyls, and substitutedalkyls, and the two nitro groups are in the 2, 4 and 2,6, positions, andsubjecting said dinitro compounds to reduction conditions selected frommolecular hydrogen with platinum on a catalyst support or molecularhydrogen with palladium on a catalyst support at pressure of between 1and 20 atmospheres at a temperature of between about 10° and 100° C. ina non-aqueous medium to produce diamino compounds of the formula:##STR16## wherein the two amino groups are in the 2,4 and 2,6 positions.5. The method of claim 4 wherein R is selected from ethyl and2-chloroethyl.
 6. The method of claim 5 wherein the diamino compound isprimarily the 2,4 compound.
 7. (Diorganooxyphosphonyl) methyldiaminobenzene of the formula: ##STR17## wherein R is an organo groupselected from alkyls having from C1 to C10 carbon atoms, phenyls andhaloalkyls having from C1 to C10 carbon atoms and where the two R groupsmay be a single alkylene having from 3 to 6 carbon atoms, and the twoamino groups are in the 2,4 or 2,6 positions.
 8. (Diorganooxyphosphonyl)methyl diaminobenzene of the formula: ##STR18## wherein R is an organogroup selected from alkyls, phenyls and substituted alkyls and the twoamino groups are in the 2,4 or 2,6 positions.
 9. (Diorganooxyphosphonyl)methyl diaminobenzene of the formula: ##STR19## wherein R is ethyl or2-chloroethyl and the two amino groups are in the 2,4 or 2,6 positions.